我有一个oracle查询,其中一部分是使用DECODE计算一些值.例如：
SELECT ...,(SELECT DECODE((SELECT 23 FROM DUAL),null,(SELECT 23 FROM DUAL))
FROM DUAL)
FROM ...
这里值“23”在运行时计算,它是非常复杂的连接 – 多个表,使用PARTITION BY等.所以我想避免在值不是“0”时执行相同的子查询.有没有办法写这样的东西
SELECT ...,(SELECT DECODE ((SELECT 23 FROM DUAL) as test,test)
FROM DUAL)
FROM ...
解决方法
这对你有用吗？
我刚刚将“23”移动到带有描述性别名的内联表中.
我刚刚将“23”移动到带有描述性别名的内联表中.
select ...,(
select
decode (
computed_value.val,computed_value.val
)
from
(select 23 as val from dual) computed_value
)
from
...
CASE声明也可能增加清晰度,如：
select
...,case when computed_value.val = 0
then null
else computed_value.val
end as my_field
from
(select 23 as val from dual) computed_value
...
